Defect inspection device and defect inspection method

ABSTRACT

A defect inspection device has: an illumination optical system which irradiates a predetermined region of an inspection target with illumination light; a detection optical system which has a detector provided with a plurality of pixels by which scattered light from the predetermined region of the inspection target due to illumination light from the illumination optical system can be detected; and a signal processing portion which is provided with a correction portion which corrects pixel displacement caused by change in a direction perpendicular to a surface of the inspection target with respect to a detection signal based on the scattered light detected by the detector of the detection optical system, and a defect determination portion which determines a defect on the surface of the inspection target based on the detection signal corrected by the correction portion.

TECHNICAL FIELD

The present invention relates to a defect inspection device and a defectinspection method for inspecting each defect on a sample surface.

BACKGROUND ART

In a production line of a semiconductor substrate, a thin-filmsubstrate, etc., inspection of defects on a surface of the semiconductorsubstrate, the thin-film substrate, etc. is performed in order to keepand improve the yield rate of products. As the background art, there isa method of “irradiating a wafer surface with a laser beam condensedinto a size of tens of micrometers, condensing and detecting scatteredlight generated from each defect, and detecting each defect having asize of from the order of tens of nanometers to the order of micrometersor more”. Patent Literature 1 (JP-A-9-304289) and Patent Literature 2(JP-A-2000-162141) have been known as the background art.

In Patent Literature 3 (JP-A-2008-268140), there has been disclosed amethod of “illuminating one and the same defect several times in oneinspection with an illuminating optical system for performing linearillumination and a detecting optical system for performing detectionwhile splitting an illumination-target region by a line sensor, andadding the scattered light to thereby improve the detectionsensitivity”.

As a method for reducing a detection error caused by change in height ofa wafer during inspection, in Patent Literature 4 (JP-A-2007-240512),there has been disclosed a method of “illuminating a surface of arotating water with a beam emitted from a first light source to form abeam spot, detecting scattered light caused by a defect such as aforeign matter on the wafer surface in a plurality of detections tooutput signals, detecting vertical motion of the wafer surface by usingwhite light or broadband light from a second light source, correctingthe position of the beam spot on the wafer surface based on informationof the vertical motion of the wafer surface to suppress coordinate errorcaused by the vertical motion of the wafer surface, correcting thedirection and position of emission of light from the first light sourceto suppress coordinate error caused by change in the first light sourceto thereby improve coordinate accuracy of the defect such as a foreignmatter to be detected, further correcting the diameter of theilluminating beam spot to suppress an individual difference in detectionsensitivity or foreign matter coordinate detection error betweendevices”.

CITATION LIST Patent Literatures

Patent Literature 1: JP-A-9-304289

Patent Literature 2: JP-A-2000-162141

Patent Literature 3: JP-A-2008-268140

Patent Literature 4: JP-A-2007-240512

SUMMARY OF THE INVENTION Technical Problem

With the recent rapid advance of miniaturization of LSI wiring, the sizeof a defect to be detected has come close to a detection limit ofoptical inspection. According to a semiconductor roadmap, massproduction of 36 nm-node LSI's will start at 2012, so that anunpatterned sample inspection device needs to have capability ofdetecting a defect with the same size as a half pitch of DRAM. Thedefect is a particle deposited on a sample as a target of inspection, acrystal originated particle (COP), a scratch generated by polishing,etc.

It has been known that the size I of scattered light generated when adefect is illuminated with a laser has the relation I∞D̂6 in which D isthe particle diameter of the defect. That is, because the scatteredlight generated thus decreases rapidly as the defect size decreases, itis necessary to increase scattered light generated from a fine defect.

Although increase of a laser output is a method of increasing scatteredlight generated from a defect, the method has a possibility that surfacetemperature of a laser irradiation portion on a sample will increase tocause damage to the sample. Although elongation of irradiation time canintensify scattered light to be detected, the inspectable area per unittime is reduced to thereby bring lowering of throughput.

For following the semiconductor miniaturization, it is necessary toimprove detection sensitivity of the inspection device intermittently.In Patent Literature 1 and Patent Literature 2, increase of laser powercan improve detection sensitivity but there is a possibility that thesample will be damaged. Although elongation of irradiation time mayimprove detection sensitivity, the inspectable area per unit time isreduced to thereby bring lowering of throughput.

To improve detection sensitivity while avoiding damage to the sample andkeeping the throughput, it is necessary to increase the signalamplification effect based on signal addition. As a method of making itpossible to detect a finer defect without causing damage to the sampleand lowering of the throughput, a method (Patent Literature 3) ofdetecting a predetermined region (one defect) several times and addingresulting signals has been conceived.

However, because the sample rotates at a high speed of several thousandRPM (Rotation Per Minute) during inspection, change in height of thesample per se in a direction perpendicular to the sample is caused byvibration or convection. In this case, a region on the sample to besubjected to laser irradiation is displaced from a region actuallysubjected to laser irradiation so that an image of scattered light isformed on a position displaced from the original position of a linesensor. Accordingly, the image of the scattered light may be formed on apixel position of the line sensor different from the predetermined pixelor may be formed as a blurred image because of defocusing. When aplurality of image-forming optical systems are disposed in directionswith respect to the sample surface, pixels for detecting scattered lightsubstantially from one and the same region are associated with eachother by adjustment at shipping so that signal addition processing isperformed based on the correspondence between pixels. That is, thereoccurs a problem that the correspondence between pixels detectingscattered light substantially from one and the same region is collapsedby change in sample height during inspection so that signals of one andthe same region cannot be added up (this problem will be hereinafterreferred to as “detection pixel displacement” or “pixel displacement”simply).

When a line sensor is used, the case where scattered light from onedefect is detected by a plurality of pixels occurs (hereinafter referredto as “pixel cracking”). In this case, the quantity of detected light islowered and detection sensitivity is lowered.

In a method described in Patent Literature 4, correction of anillumination position in accordance with change in wafer height has beendisclosed. When an image-forming optical system is used, it is howevernecessary not only to correct the illumination position but also tocorrect the distance between the wafer and the image-forming opticalsystem. This method cannot avoid detection pixel displacement caused bychange in wafer height.

An object of the invention is to provide a defect inspection device anda defect inspection method for avoiding the influence of detection pixeldisplacement to make it possible to add up scattered light generatedsubstantially from one and the same region.

Solution to Problem

The summary of the representative one s of the inventions disclosed inthis application will be explained briefly as follows.

(1) A defect inspection device including: an illumination optical systemwhich irradiates a predetermined region of an inspection target withillumination light; a detection optical system which has a detectorprovided with a plurality of pixels by which scattered light from thesurface of the inspection target due to illumination light from theillumination optical system can be detected; a correction portion whichcorrects pixel displacement caused by change in a directionperpendicular to a surface of the inspection target with respect to adetection signal based on scattered light detected by the detector ofthe detection optical system, and a detection portion which detects adefect on the surface of the inspection target based on the detectionsignal corrected by the correction portion.

(2) In the defect inspection device described in (1), a plurality ofdetectors are provided in the detection optical system so that thedetectors can detect scattered light from the surface of the inspectiontarget in different azimuth angle directions with respect to the surfaceof the inspection target, respectively; and the correction portioncorrects the pixel displacement with respect to a plurality of detectionsignals based on scattered light detected by the plurality of detectorsrespectively, wherein the device further includes an adding portionwhich adds the plurality of detection signals corrected by thecorrection portion.

Advantageous Effects of Invention

According to the invention, it is possible to provide a defectinspection device and a defect inspection method which can inspect eachfine defect on a sample surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of a first embodiment of a defect inspection deviceaccording to the invention;

FIG. 2 is a side view of the first embodiment of the defect inspectiondevice according to the invention;

FIG. 3 shows a detection optical system in the first embodiment of thedefect inspection device according to the invention;

FIG. 4 is a side view of the detection optical system in the firstembodiment of the defect inspection device according to the invention;

FIG. 5 is a view for explaining the spatial position relation between anillumination region and a line sensor and the position relation betweenthe illumination region and the line sensor with respect to a detectionrange on a sample surface;

FIG. 6 is a view for explaining the position relation between theillumination region and the detection range on the sample surface;

FIG. 7 is a view for explaining the position relation between theillumination region and the detection range on the sample surface;

FIG. 8 is a view for explaining the position relation between theillumination region and the detection range on the sample surface;

FIG. 9 is a view for explaining a detection signal;

FIG. 10 is a view showing the relation between each line sensor and theposition where an image of defect scattered light is formed;

FIG. 11 is a view showing the relation between each line sensor and theposition where an image of defect scattered light is formed;

FIG. 12 is a view for explaining a defect map and a Haze map;

FIG. 13 is a view of the first embodiment of the defect inspectiondevice according to the invention;

FIG. 14 is a flow of inspection in the first embodiment;

FIG. 15 is a view of a second embodiment of a defect inspection deviceaccording to the invention;

FIG. 16 is a view for explaining a sensor in the second embodiment;

FIG. 17 is a view showing the relation between the detection range of aline sensor and the feed pitch;

FIG. 18 is a view showing the relation between the detection range of aline sensor and the feed pitch;

FIG. 19 is a view for explaining sub-pixel addition;

FIG. 20 is a view for explaining sub-pixel addition; and

FIG. 21 is a flow of inspection in the second embodiment.

DESCRIPTION OF EMBODIMENTS

An embodiment of a defect inspection device according to the inventionwill be described with reference to FIGS. 1 and 2 by way of example. Thedefect inspection device shown in FIGS. 1 and 2 has an illuminationoptical system 101, detection optical systems 102 a to 102 f, a samplestage 103, and a signal processing portion 104. FIG. 1 is a plan view(top view) of the inspection device. FIG. 2 is a side view of theillumination optical system 101, the detection optical system 102 a andthe sample stage 103.

The illumination optical system 101 has a laser light source 2, a beamexpander 3, a polarizing element 4, mirrors m, and a condensing lens 5.The beam diameter of a laser beam 200 emitted from the laser lightsource 2 is adjusted to a desired size by the beam expander 3. The laserbeam 200 is then converted into a desired polarized state by thepolarizing element 4 and irradiated at an elevation angle θi on aninspection-target region of a sample 1 by the condensing lens 5 throughthe reflection mirrors m.

Here, the laser light source 2 is a laser light source which oscillatesa laser beam with a wavelength of 355 nm, and the illumination elevationangle θi is an angle of 10 degrees from the sample surface. Anillumination region 20 is substantially shaped like an ellipse on thesample surface and has a size of about 1000 μm in the major axisdirection and about 20 μm in the minor axis direction.

The beam expander 3 is an anamorphic optical system constituted by aplurality of prisms. The beam expander 3 changes the beam diameter inonly one direction in a plane perpendicular to the optical axis so thatthe sample 1 is subjected to spot illumination or linear illumination bythe condensing lens 5.

The detection optical systems 102 a to 102 f are arranged in directionsof different azimuth angles φ and detect scattered light generated fromthe illumination region 20 on the sample. The detection optical systems102 a to 102 f are arranged at intervals of about 60 degrees in terms ofthe directions of azimuth angles. The azimuth angles φ at which thedetection optical systems 102 a to 102 f are arranged are 30, 90, 150,210, 270 and 330 degrees respectively.

The detection optical system 102 a is arranged in the direction of anelevation angle θs with respect to the sample surface. The detectionelevation angle θs is an angle of 30 degrees with respect to the samplesurface. The numerical aperture is 0.3. The same rule is applied to thedetection optical systems 102 b to 102 f. Each of the detection opticalsystems 102 b to 102 f is arranged at the detection elevation angle of30 degrees with respect to the sample surface, and the numericalaperture is 0.3.

The detection optical systems 102 a to 102 f have substantially the sameconfiguration. Details of the configuration of each of the detectionoptical systems 102 a to 102 f are shown in FIG. 3. Each of thedetection optical systems 102 a to 102 f has an objective lens 10, apolarizing element 11, an image-forming lens 12, and a line sensor(detector) 13. The objective lens 10 is a reducing system having anoptical magnification of 0.1.

For example, the polarizing element 11 is a polarizing filter, a PBS(Polarized Beam Splitter) or the like. The polarizing element 11 reducesscattered light (referred to as “roughness scattered light”) generatedfrom fine roughnesses of the sample surface by polarization detection sothat finer defects can be detected. The polarizing element 11 can rotatearound the optical axis of the detection optical system and can bedetached and attached. NSPFU-30C made by SIGMA KOKI Co., Ltd. may beused as the polarizing filter. PBSW-10-350 etc. made by SIGMA KOKI Co.,Ltd. may be used as the PBS.

The line sensor 13 can detect scattered light with respect to aplurality of pixels. 25S3923256Q etc. made by Hamamatsu Photonics K.K.may be used as the line sensor 13. The number of pixels of 25S3924-256Qis 256, the pixel pitch thereof is 25 μm, and the pixel height thereofis 0.5 mm.

The illumination region 20 and the line sensor 13 have a conjugateposition relation, so that an image of scattered light from theillumination region 20 is formed on each of pixels of the line sensor13. When the line sensors of the detection optical systems 102 a and 102d are arranged so as to be substantially parallel with a longitudinaldirection 210 of the illumination region 20, the line sensors and theillumination region 20 have a conjugate position relation. Because thedetection optical system 102 b is arranged in a direction with anazimuth angle of 30 degrees and an elevation angle of 30 degrees, animage is formed on an image surface 15 inclined at 30 degrees withrespect to the optical axis as shown in FIG. 4 when image formation isperformed in the condition of an optical magnification of 1. To correctthe inclination of the image and form an image on a surfacesubstantially perpendicular to an optical axis 212, the detectionoptical system may be provided as a reducing system having amagnification. Because the objective lens 10 is a reducing system havingan optical magnification of 0.1, the inclination of the image iscorrected so that an image is formed on an image plane 16 substantiallyperpendicular to the optical axis 212. The total optical magnificationis determined based on the magnification of each image-forming lens 12,so that the total optical magnification of the detection optical systems102 a to 102 f is 10.

When the line sensor 13 of the detection optical system 102 b isarranged in the plane 16 perpendicular to the optical axis and in aposition parallel to the sample 1, the illumination region 20 on thesurface of the sample 1 and a detection range 17 of the line sensor 13have a position relation as shown in FIG. 5, so that an angle of 30degrees is formed between the longitudinal direction 210 of theillumination region 20 and a direction 213 of arrangement of pixels ofthe line sensor. In this state, it is necessary to rotate the linesensor around the optical axis 212 because all scattered light generatedfrom the illumination region 20 cannot be supplemented. The anglebetween the longitudinal direction 210 of the illumination region 20 andthe direction 213 of arrangement of the pixels of the line sensor is 30degrees. Therefore, when the line sensor is rotated by the same angle of30 degrees, the angle between the longitudinal direction 210 of theillumination region 20 and the direction 213 of arrangement of thepixels of the line sensor can be about 0 degrees so that all scatteredlight generated from the illumination region 20 can be supplemented andan image can be formed on the line sensor. With respect to the detectionoptical systems 102 b, 102 c, 102 e and 102 f, the angle between thelongitudinal direction 210 of the illumination region 20 and thedirection 213 of arrangement of the pixels of the line sensor variesaccording to the detection azimuth angle. Therefore, each line sensor isrotated around the optical axis in accordance with the detection azimuthangle so that all scattered light generated from the illumination region20 is supplemented and an image is formed on the line sensor.

The sample stage 103 in FIG. 2 includes a chuck (not shown) for holdingthe sample 1, a Z stage (not shown) for performing height control, arotation stage 6 for rotating the sample, and a translation stage 7 formoving the sample 1 in an R direction. The sample stage 103 performsrotational scanning and translational scanning to thereby scan theillumination region 20 so that the whole surface of the sample 1 isilluminated spirally. Here, the height of the sample surface in astationary state is defined as z=0 and the vertically upward directionis defined as a positive direction.

The signal processing portion 104 in FIG. 1 is provided with an analogcircuit 150, an A/D conversion portion 151, an adjacent pixelintegration portion (pixel displacement correction portion) 152, asignal addition/defect determination portion 153, a CPU 154, a mapoutput portion 155, and an input portion 156.

The reason why pixel displacement occurs based on change in sampleheight will be described below with reference to FIGS. 6 and 7.

FIG. 6 shows the position relation between a detection range 21 a of theline sensor and the illumination region 20 on the surface of the sample1 viewed from a detection azimuth angle at which the detection opticalsystem 102 a is arranged. FIG. 7 shows the position relation between adetection range 21 b of the line sensor and the illumination region 20on the surface of the sample 1 viewed from a detection azimuth angle atwhich the detection optical system 102 b is arranged. Here, thedirection of arrangement of the pixels of the line sensor is defined asR1, and the direction of height of the pixels is defined as R2. R1 andR2 cross each other at right angles.

When there is no change in sample height, the position relation betweenthe illumination region 20 and the detection range 21 a in FIG. 6 andthe position relation between the illumination region 20 and thedetection range 21 b in FIG. 7 are the same. In this state, thedetection ranges of the two line sensors are initially adjusted to besubstantially one and the same region. That is, correspondence of pixelsfor detecting scattered light substantially generated from one and thesame region is determined in the initial adjustment, so that scatteredlight signals may be added in accordance with the correspondence duringinspection.

The case where change in sample height occurs will be described next.When the height of the sample surface is a height of z=0, theillumination region 20 and the line sensor 13 are adjusted in focus.However, when the height of the sample surface changes, the positionwhere an image of scattered light generated from the illumination region20 is formed on the line sensor changes because the illumination region20 and the line sensor 13 are out of focus. Assume that “h” is anarbitrary constant. It is shown that the illumination region 20 isdisplaced to the position of an illumination region 20′ when the heightof the sample surface is shifted by +h μm in a z direction because thesample 1 rotates at a high speed, and that the illumination region 20 isdisplaced to the position of an illumination region 20″ when the heightof the sample surface is shifted by −h μm in the z direction because thesample 1 rotates at a high speed.

In the example of FIG. 6, a direction 25 of displacement of theillumination region 20 is only one direction parallel to the pixelheight direction R2. In this case, there is no occurrence of pixeldisplacement. On the other hand, in the example of FIG. 7, a direction26 of displacement of the illumination region 20 is displaced not onlyin a direction parallel to R2 but also in a direction parallel to R1.Because the illumination region 20 is also displaced in the R1direction, pixel displacement occurs. The correspondence of pixels setby the initial adjustment for detecting scattered light substantiallygenerated from one and the same region is collapsed by occurrence ofpixel displacement, so that the effect of signal amplification based onsignal addition is reduced.

It has been known that the direction 25 or 26 of displacement of theillumination region 20 based on change in sample height varies accordingto the detection azimuth angle φ, and that the magnitude of displacementof the illumination region 20 varies according to the detectionelevation angle θs, the detection azimuth angle φ and the magnitude ofchange in sample height.

While the direction of displacement of the illumination region 20 ishereinafter regarded as a vector decomposed into two components of R1and R2, the sign of the R1 component is defined as the direction ofpixel displacement, and the absolute value of the R1 component isdefined as the magnitude of pixel displacement. On the assumption of adirection 27 of displacement of the illumination region 20 in the caseof FIG. 8, the direction of pixel displacement is negative (−: minus)and the magnitude of pixel displacement is the length of a line segmentOA.

In the invention, when the correspondence of pixels for detectingscattered light substantially generated from one and the same region iscollapsed by occurrence of pixel displacement, signals of adjacentpixels in the line sensor are processed integrally in the followingmanner so that signals substantially from one and the same region can beadded.

The line sensor 13 generates an electric signal in accordance with thequantity of received light. The electric signal is led into the analogcircuit 150. Processing performed by the analog circuit 150 will bedescribed below.

When scattered light generated from the illumination region 20 isdetected, a signal as shown in FIG. 9 is outputted from the line sensor13. Roughness scattered light N₀ generated from roughnesses of thesample surface is always generated during a laser irradiation period anddetected as low-frequency undulation (<the order of kHz). When roughnessscattered light N₀ incident on the line sensor 13 is convertedphotoelectrically, shot noise n₀ is generated as random change anddetected at the same time. On the other hand, defect scattered light S₀generated from defects is high in frequency (>the order of kHz) comparedwith the roughness scattered light because the defect scattered light S₀is generated in pulses only for a short period when the illuminationregion 20 with an illumination width of 20 μm passes through eachposition where a defect is located. That is, when the detection signalshown in FIG. 9 is led into the analog circuit 150, a high-pass filter(pass band: >the order of kHz) is applied to the detection signal tothereby make it possible to extract a defect signal and a low-passfilter (pass band: <the order of kHz) is applied to the detection signalto thereby make it possible to extract the intensity of roughnessscattered light (hereinafter referred to as Haze signal).

From the above description, the high-pass filter is applied to theelectric signal generated based on the defect scattered light detectedby the line sensor 13 while the low-pass filter is applied to theelectric signal generated based on the roughness scattered lightdetected by the line sensor 13. Consequently, the defect signal and theHaze signal can be processed separately.

The signals subjected to the aforementioned filtering processes areconverted into digital signals at a sampling pitch not lower than theorder of MHz by the A/D conversion portion 151. The defect signalconverted into the digital signal is led into the adjacent pixelintegration portion (pixel displacement correction portion) 152 in whichsignals of adjacent pixels are integrated (pixel displacement iscorrected).

A method of signal integration will be described with reference to FIG.10. FIG. 10 shows the position relation between pixels of the linesensor 13 and a pixel on which an image of defect scattered light 33 isformed. The case where an image of defect scattered light 33 is formedsubstantially in the center of a pixel C in each line sensor when thereis no occurrence of change in sample height will be described by way ofexample while eight pixels (A to H) in each of the line sensors 30, 31and 32 used in the detection optical systems 102 f, 102 a and 102 brespectively are taken up as a subject for discussion.

(1) In a state where change in sample height does not occur or is toosmall to cause pixel displacement, detection signals of the pixels C inall the line sensors may be added up.

(2) When pixel displacement of about one pixel occurs in the case wherechange in sample height occurs in the +z direction, defect scatteredlight 33 is still detected by the pixel C of the line sensor 31 butdefect scattered light 33 is detected by the pixel B of the line sensor30 and detected by the pixel D of the line sensor 32. That is, detectionsignals of the pixel B in the line sensor 30, the pixel C in the linesensor 31 and the pixel D in the line sensor 32 may be added up.

(3) In a state where an image of defect scattered light is formedsubstantially in the center of the pixel C, detection signalssubstantially from one and the same region can be detected in spite ofoccurrence of change in sample height as long as output signals of therespective line sensors are subjected to the aforementioned process (1)or (2) by parallel processing. However, a case where an image of defectscattered light is formed out of the center of the pixel may beconceived. In addition, a case where the magnitude of pixel displacementis not larger than one pixel may be conceived. The case shown in FIG. 11is therefore assumed. In the line sensor 31, pixel displacement does notoccur but an image of defect scattered light 33 is formed in a place outof the center of the pixel. Because the magnitude of pixel displacementis not larger than one pixel, pixel displacement occurs in the linesensor 30 so that an image of defect scattered light is detected by thepixel B of the line sensor 30, but pixel displacement does not occur inthe line sensor 32 so that an image of defect scattered light isdetected by the pixel C of the line sensor 32. In this case, signalssubstantially from one and the same region cannot be added up only bythe aforementioned processes (1) and (2).

(4) In the case of (3), detection signals of adjacent pixels may besubjected to an integration process. In the line sensor 30, detectionsignals of the pixels B and C are integrated so that detection signalsof two pixels are processed as one detection signal. In the line sensor32, detection signals of the pixels C and D are processed integrally. Inthe line sensor 31, detection signals of the pixels B, C and D areprocessed integrally. Incidentally, integration is performed while thedetection signals of the pixels B and D are multiplied by a weight of0.5. By integrally processing signals of adjacent pixels in this manner,scattered light substantially from one and the same region can be addedup in all the cases of (1) to (3).

(5) The case where the magnitude of pixel displacement is not smallerthan two pixels may be conceived. In this case, the combination ofpixels to be integrated may be changed. In the line sensor 30, detectionsignals of the pixels A and B are integrated. In the line sensor 32,detection signals of the pixels D and E are integrated. In the linesensor 31, the same integration as (4) may be performed. Because thecombination of pixels to be integrated is changed in accordance with themagnitude of pixel displacement as described above, patterns of thequantity of change of pixel displacement are prepared while themagnitudes of change in sample height allowed to be generated inaccordance with the performance of the inspection device are grasped orthe magnitudes of change in sample height are really measured with asensor to thereby determine the quantity of change of pixel displacementso that the influence of pixel displacement can be avoided when thequantity of change of pixel displacement is calculated by parallelprocessing. When patterns of the quantity of change of pixeldisplacement are prepared, detection signals corresponding to thepatterns respectively are subjected to an integration process and, forexample, a pattern having the highest SN is selected so that the optimumquantity of pixel displacement can be determined

(6) Although the items (1) to (5) have been described in the case wherethe sample height changes in the +z direction, there may be the casewhere the sample height changes in the −z direction. In this case, thecombination of pixels to be integrated may be changed because pixeldisplacement occurs in the opposite direction. For example, when thesample height changes in the −z direction so that pixel displacement byabout one pixel occurs, detection signals of the pixels C and D in theline sensor 30 may be integrated and detection signals of the pixels Band C in the line sensor 32 may be integrated. The line sensor 31 may beprocessed in the same manner as (4).

(7) As described above, integration processes are performed with aplurality of combinations and threshold processes are performed on thecombinations respectively so that only signals in the case where defectsare detected may be used.

(8) Although the aforementioned (1) to (7) have been described only fordefect signals, the same processing is performed on Haze signals.Although description has been made on three kinds of detection signalsby way of example, the aforementioned processing is performed on alldetector signals.

The integrated signals are led into the signal addition/defectdetermination portion 153. Signals of one and the same coordinates areadded up, so that defect determination, defect classification and defectsize calculation due to threshold processes and Haze processing due tolevel determination are performed based on the sum signals.

A defect map 160 and a Haze map 161 shown in FIG. 12 are displayed bythe map output portion 155 through the CPU 154. The defect map 160 isdisplayed based on defect type, defect size and detection coordinatesfetched at inspection time. The Haze map 161 is displayed based on Hazesignal level and detection coordinates fetched at inspection time. Theinput portion 156 includes a user interface through which a user canperform recipe setting etc.

The advantages of presence of detection optical systems at a pluralityof azimuth angles are not only in that the signal amplification effectbased on signal addition can be increased but also in that defectdetection sensitivity can be improved when detection optical systems tobe used are selected or detection signals in the respective detectionoptical systems are used while weighted. The roughness scattered lighthas azimuth angle dependence which depends on the roughness state of thesample surface. For example, a sample such as Si having a very smoothsurface in terms of surface roughness has a tendency to generateroughness scattered light intensively in a direction of incidence of thelaser beam 200, that is, in a direction of the azimuth angle at whicheach of the detection optical systems 102 e and 102 f is located. Asample such an Al deposition film having a large surface roughness has aproperty to generate roughness scattered light intensively in adirection of movement of the laser beam 200, that is, in a direction ofthe azimuth angle at which each of the detection optical systems 102 band 102 c is located. When only detection signals detected by defectdetection optical systems located at azimuth angles for generatingroughness scattered light weakly are used or processing is performed insuch a manner that weights corresponding to the magnitudes of roughnessscattered light are multiplied as gains by the detection signals, defectdetection sensitivity can be improved.

Although laser illumination is performed in a direction parallel to thelongitudinal direction 210 of illumination in FIG. 1, the direction oflaser irradiation need not be substantially the same as the longitudinaldirection 210 of illumination, that is, illumination may be performed indifferent azimuth angle directions. The advantage of illumination indifferent directions is in that classification performance of defectshaving directivities in terms of defect shape such as scratches can beimproved. Scattered light generated from a defect such as COPsubstantially symmetric with respect to the azimuth angle direction doesnot have azimuth angle dependence but has a tendency to be generatedsubstantially evenly in all azimuth angle directions. On the other hand,scattered light generated from a defect such as a scratch asymmetricwith respect to the azimuth angle direction has azimuth angledependence. Moreover, because the azimuth angle characteristic ofscattered light generated from a scratch depends on an azimuth angle ofincidence of illumination, defect classification accuracy and sizecalculation accuracy can be improved when the direction of illuminationis changed actively and signals of detection systems located inrespective azimuth angle directions are compared.

FIG. 13 is an example of a side view of the embodiment shown in FIG. 1.An oblique illumination optical system 101 for performing illuminationat a low elevation angle θi, a low angle detection optical system 102 gfor performing scattered light detection in a low elevation angledirection θs and a detection optical system 102 h for performingdetection at a higher elevation angle than that of the low angledetection optical system are provided in FIG. 13.

The illumination elevation angle θi of the oblique illumination opticalsystem 101 is 10 degrees with respect to the sample surface. As anoblique illumination optical system, a perpendicular illuminationoptical system for illuminating the sample substantially in aperpendicular direction may be provided (not shown).

The elevation angle at which the low angle detection optical system 102g is arranged is 30 degrees whereas the elevation angle at which thehigh angle detection optical system 102 h is arranged is 60 degrees.Both the numerical aperture of the low angle detection optical system102 g and the numerical aperture of the high angle detection opticalsystem 102 h are 0.3.

The detection signals are inputted to the analog circuit 150, separatedinto defect signals and Haze signals by the high-pass filter and thelow-pass filter and converted into digital signals at a sampling pitchof the order of MHz or higher by the A/D conversion portion 151. Thedigital signals generated by the conversion are led into the adjacentpixel integration portion (pixel displacement correction portion) 152and corrected based on set combinations (patterns) of the quantity ofchange of pixel displacement. The correction results are subjected tothreshold processing or the like so that, for example, a pattern havingthe highest S/N as a result is selected. The detection signals areintegrated based on the quantity of change of pixel displacement (pixeldisplacement quantity) of the selected pattern. In the integratedsignals, signals of one and the same coordinates are added up in thesignal addition/defect determination portion 153. The signaladdition/defect determination portion 153 performs defect determination,defect classification and defect sizing due to threshold processing andHaze processing due to level determination based on the sum signal.Then, the defect map 160 and the Haze map 161 shown in FIG. 12 aredisplayed by the map output portion 155 through the CPU 154. The defectmap 160 is displayed based on defect signals and coordinates fetched atinspection time. The Haze map 161 is displayed based on Haze signals andcoordinates fetched at inspection time. The input portion 156 includes auser interface through which a user can perform recipe setting etc.

The embodiment in which an illumination optical system and a detectionoptical system are located in different elevation angle directions hasbeen described above. There are two advantages as follows.

When a particle deposited on the sample is illuminated by the obliqueillumination optical system, the scattering sectional area of theparticle can be increased compared with the perpendicular illuminationoptical system. Accordingly, the quantity of scattered light generatedfrom the particle increases so that a finer defect can be detected.Scattered light from a defect having a size of tens of nm is intensivelyscattered on the low elevation angle side whereas scattered light from adefect having a size of 100 nm or larger is intensively scattered on thehigh elevation angle side. Accordingly, when a fine defect is detectedby the low elevation angle detection optical system while a relativelylarge defect is detected by the high elevation angle detection opticalsystem, the range of defect size which can be detected can be enlarged.

On the other hand, with respect to a concave defect such as a COP or ascratch of the sample, the scattering sectional area of the defect canbe increased to improve sensitivity for the concave defect when thedefect is illuminated by the perpendicular illumination optical system.Because scattered light from the concave defect is intensively scatteredon the high elevation angle side, detection sensitivity can be improvedfurther when the high elevation angle detection optical system is used.

As described above, the intensity distribution and elevation anglecharacteristic of scattered light generated from each defect variesaccording to the defect type (particle, COP, scratch, etc.) or size.Accordingly, when signals according to illumination directions anddetection directions are combined and compared, defect classificationaccuracy and defect size calculation accuracy can be improved.

As a method of processing respective detector signals in directions of aplurality of azimuth angles and a plurality of elevation angles,respective detection signals are added or averaged. By adding thedetection signals, the quantity of detection light increases to bring aneffect in improving detection sensitivity. By averaging the detectionsignals, the width of size which can be detected within a dynamic rangeof the sensor increases to bring an effect in enlarging the dynamicrange.

A flow of defect detection processing will be described below withreference to FIG. 14.

First, a sample 1 is set on the stage and an inspection recipe is set(step 170). Inspection is started (step 171), and a defect signal and aHaze signal are detected (step 172). With respect to signals ofrespective detectors, signals of adjacent pixels are subjected tointegration processing (step 173). On this occasion, the detectionsignals are corrected based on predetermined patterns of the quantity ofpixel displacement respectively and the correction results are subjectedto threshold determination so that, for example, a pattern having thehighest S/N as a correction result is determined as the quantity ofpixel displacement. In the signal addition/defect determination portion153, signals of one and the same coordinates are added up (step 174).Defect determination, defect classification, size calculation and Hazeprocessing are performed based on the sum signal (step 175), so that thedefect map and the Haze map are displayed (step 176).

Although description has been made in the case where the laser lightsource 2 is a light source which oscillates a wavelength of 355 nm, thelaser light source 2 may be a laser light source which oscillates avisible, ultraviolet or vacuum ultraviolet laser beam.

Although description has been made in the case where the illuminationregion 20 is substantially shaped like an ellipse on the sample surfaceand has a size of about 1000 μm in the major axis direction and about 20μm in the minor axis direction by way of example, the illuminationregion 20 need not be shaped like an ellipse and the size of theillumination region 20 is not limited.

Although the embodiment in which six detection optical systems arelocated in different azimuth angle directions φ has been described withreference to FIG. 1, the number of detection optical systems need not belimited to six. The detection azimuth angle φ and the detectionelevation angle θs are not limited.

Although description has been made in the case where the objective lens10 has an optical magnification of 0.1 by way of example, themagnification is not limited. Although description has been made in thecase where the total optical magnification of the detection opticalsystems 102 a to 102 f is 10 by way of example, the total opticalmagnification is not limited.

The numerical apertures of the detection optical systems 102 a to 102 fneed not be all substantially the same or need not be different from oneanother.

Although description has been made in the case where the illuminationoptical system 101 performs illumination by the combination of theexpander 3 and the condensing lens 5 by way of example, a cylindricallens may be used for linear illumination. When a cylindrical lens isused singly, linear illumination can be applied on the sample withoutuse of any anamorphic optical system for changing the beam diameter inonly one direction in a plane perpendicular to the optical axis.Accordingly, the beam expander 3 can be dispensed with, so as to beeffective in making the optical system slimmer.

The line sensor 13 is used for receiving scattered light and performingphotoelectric conversion. A multi-anode photomultiplier tube, a TVcamera, a CCD camera, a photodiode, a linear sensor or a highlysensitive image sensor etc. obtained by combining an image intensifierwith these may be used as the line sensor 13. For example, use of atwo-dimensional sensor permits a wide region to be inspected at a time.

Although description has been made in the case where the line sensor has256 pixels with a pixel size of 25 μm, the number of pixels and thepixel size are not limited.

A plurality of low angle detection optical systems 102 g and a pluralityof high angle detection optical systems 102 h are located in differentazimuth angle directions φ, and the elevation angles at which thesedetection optical systems 102 g and 102 h are arranged need not be allsubstantially the same or need not be different from one another.

The numerical apertures of the low angle detection optical systems 102 gand the high angle detection optical systems 102 h need not be allsubstantially the same or need not be different from one another.

A second embodiment of the invention will be described with reference toFIG. 15. In FIG. 15, an illumination optical system 101, a detectionoptical system 102, a sample stage 103, a signal processing portion 104and a regularly reflected light observation optical system 105 areprovided. The illumination optical system 101 is constituted by a laserlight source 2, a beam expander 3, a polarizing element 4, and acondensing lens 5. The beam diameter of a laser beam 200 emitted fromthe laser light source 2 is adjusted to a desired diameter by the beamexpander 3. The laser beam 200 is then converted into a desiredpolarized state by the polarizing element 4 and an inspection-targetregion of a sample 1 is illuminated with the laser beam 200 by thecondensing lens 5 through reflection mirrors m.

On this occasion, a laser light source which oscillates a visible,ultraviolet or vacuum ultraviolet laser beam may be used as the laserlight source 2. An illumination elevation angle θi of the obliqueillumination optical system 101 is 10 degrees with respect to the wafersurface.

The beam expander 3 is an anamorphic optical system constituted by aplurality of prisms. The beam diameter is changed in only one directionin a plane perpendicular to the optical axis, so that spot illuminationor linear illumination is applied on the wafer 1 by use of thecondensing lens 5.

The detailed configuration of the detection optical system 102 issubstantially the same as that shown in FIG. 3. The detection opticalsystem 102 is constituted by an objective lens 10, a polarizing element11, an image-forming lens 12, and a line sensor 13. An image ofscattered light generated from an illumination region 20 is formed oneach pixel of the line sensor 13.

The detection optical system 102 is arranged in the direction of anelevation angle θs. Detection is performed at the detection elevationangle θs which is 30 degrees with respect to the wafer surface. Thenumerical aperture is 0.3.

The sample stage 103 is constituted by a chuck (not shown) for holdingthe sample 1, a Z stage (not shown) for performing height control, arotation stage 6 for rotating the sample, and a translation stage 7 formoving the sample 1 in an R direction. The sample stage performsrotational scanning and translational scanning to thereby scan theillumination region 20 so that the whole surface of the sample 1 isilluminated spirally.

The signal processing portion 104 has an analog circuit 150, an A/Dconversion portion 151, a pixel displacement detection portion 157, acoordinate correction portion 158, a signal addition/defectdetermination portion 159, a CPU 154, a map output portion 155, and aninput portion 156.

The line sensor 13 generates an electric signal in accordance with thequantity of received light. The electric signal is led into the analogcircuit 150. In the analog circuit 150, the electric signal is separatedinto a defect signal and a Haze signal by a high-pass filter or alow-pass filter, and converted into digital signals at a sampling pitchof the order of MHz or higher by the A/D conversion portion 151.

The regularly reflected light observation optical system 105 is disposedin a direction of movement of regularly reflected light 201 and has acondensing lens 5 and a PSD (sensor) 52 (Position Sensitive Detector).S3932 etc. made by Hamamatsu Photonics K.K. may be used as the PSD(sensor) 52.

The second embodiment is characterized in that the magnitude anddirection of position displacement of the regularly reflected light 201are detected by the regularly reflected light observation optical system105 to thereby detect change in sample height, the magnitude anddirection of pixel displacement are calculated based on the magnitudeand direction of change in sample height by the pixel displacementdetection portion 157, and coordinate correction is performed by thecoordinate correction portion 158.

FIG. 16 is an enlarged view of a side of a region where the laser beam200 in FIG. 15 is incident on the sample 1 at an elevation angle θi andregularly reflected light 201 of the laser beam 200 is incident on thePSD (sensor) 52. FIG. 16 shows the case where the surface height of thesample changes by z=−h μm. When the sample height changes as shown inFIG. 16, the position of the regularly reflected light incident on thePSD (sensor) 52 changes. An electric signal corresponding to theincidence position is outputted from the PSD (sensor) 52. Accordingly,displacement of the position of incidence of the regularly reflectedlight due to change in sample height can be detected while the positionof incidence of the regularly reflected light 201 at the position of thesample surface height z=0 is used as a reference. When X is themagnitude of displacement in regularly reflected light detectionposition outputted from the PSD (sensor) 52, X has the relation asfollows.

X=2·h·cos θi   (Expression 1)

When the magnitude X of displacement of the detection position of theregularly reflected light 201 from the sample 1 is detected by theregularly reflected light observation optical system 105 and the(Expression 1) is used, the magnitude h and direction (upward ordownward) of change in sample height can be calculated.

The magnitude and direction of change in sample height detected by theaforementioned regularly reflected light observation optical system 105are inputted to the pixel displacement detection portion 157. Themagnitude and direction of pixel displacement can be calculatedgeometrically based on trigonometric functions by use of threeparameters, that is, the azimuth angle direction φ and the elevationangle direction θs in which each detection optical system is disposed,and the magnitude h of change in sample height. The magnitude P of pixeldisplacement is represented as follows.

P=h·sin θs/tan φ  (Expression 2)

In the pixel displacement detection portion 157, the magnitude anddirection of pixel displacement are calculated in accordance with eachdetection optical system based on the parameters of the azimuth angle φ,the elevation angle θs and the magnitude h of change in sample heightbased on the (Expression 2), so that a coordinate correction signal isgenerated and outputted to the coordinate correction portion 158.

A specific example of the coordinate correction signal will be describedbelow. Assume that a coordinate system has two axes (R, θ). Consider thecase where change in sample height occurs at θ=θ₀ (arbitrary constant)and occurrence of pixel displacement of “+5 μm in the R direction” isdetected by the aforementioned method. The coordinate correction signalin this case is as follows. As for detection signals of all pixels inthe detection optical system 102 b, the R-direction coordinate incoordinates at θ=θ₀ is corrected only by “−5 μm”.

The defect signal and the Haze signal are inputted from the A/Dconversion portion 151 to the coordinate correction portion 158 and thecoordinate correction signal is inputted from the pixel displacementdetection portion 157 to the coordinate correction portion 158.Coordinates of each of the defect signal and the Haze signal arecorrected based on the coordinate correction signal. Thecoordinate-corrected signals are led into the signal addition/defectdetermination portion 159. Contents of processing in the signaladdition/defect determination portion 159 will be described below.

In the invention, detection regions are inspected so as to overlap oneanother and scattered light signals from one and the same region areadded up so that S/N can be improved. On this occasion, the distance ofradial movement in accordance with one rotation of the sample is calledfeed pitch. By changing the feed pitch, detection sensitivity andinspection speed can be controlled and description will be made withreference to FIG. 17. FIG. 17 shows the detection position of the linesensor 13 on the sample surface with one detection system used as asubject. The case where a line sensor having eight pixels is used isassumed here. Pay attention to a region detected by a pixel A in thefirst rotation. When the feed pitch is set to be equal to the size ofone pixel, scattered light substantially from one and the same region isdetected by an adjacent pixel B in the second rotation. Thereafter,scattered light substantially from one and the same region is detectedby each pixel C→D→E→F→G→H whenever one rotation is made. When thesesignals substantially from one and the same region are added up, S/N canbe improved. When the size of the feed pitch is set to be equal to thesize of eight pixels as shown in FIG. 18, the area which can beinspected per unit time can be increased to eight times compared withFIG. 17 so that the inspection speed can be shortened. However, the casewhere defect scattered light is detected by two pixels may occur (pixelcracking). In this case, the quantity of detection light is lowered sothat S/N is lowered. It is impossible to avoid this entirely as long asthe feed pitch is an integer multiple of the pixel size.

In the second embodiment, scanning is performed in the condition thatthe feed pitch is shifted from an integer multiple of the number ofpixels, and signals of pixels in a common portion of the detectionregion are added up in the signal addition/defect determination portion159 to thereby make it possible to suppress lowering of S/N caused bypixel cracking. Description will be made below. In FIG. 19, it isassumed that a line sensor having eight pixels is used. The feed pitchhas a size of 8/3 pixels. The R-direction pixel size on the samplesurface is 5 μm.

Pay attention to a region on the sample surface detected by the pixel Bin the first rotation. Because the feed pitch is not an integer multipleof the pixel size, there is no combination of pixels in which detectionregions entirely coincide with each other. It is known that detection ismade by the pixels D and E in the second rotation and detection is madeby the pixels G and H in the third rotation. In this case, signaloutputs of a region detected by the respective pixels may be subjectedto addition processing as follows.

-   (a) An output of a region detected by the pixel B in the first    rotation+an output of a region detected by the pixel E in the second    rotation+an output of a region detected by the pixel H in the third    rotation→detection signal in a region 80-   (b) An output of a region detected by the pixel B in the first    rotation+an output of a region detected by the pixel E in the second    rotation+an output of a region detected by the pixel G in the third    rotation→detection signal in a region 81-   (c) An output of a region detected by the pixel B in the first    rotation+an output of a region detected by the pixel D in the second    rotation+an output of a region detected by the pixel G in the third    rotation→detection signal in a region 82

A process of performing scanning in the condition that the feed pitch isshifted from an integer multiple of the pixel size, and applyingintegration processing to signals of pixels in which a common portion ofthe detection region is present is hereinafter referred to as sub-pixeladdition.

The reason why sub-pixel addition can suppress lowering of S/N caused bypixel cracking is as follows. The case where pixel cracking of defectscattered light between the pixels D and E occurs in the second rotationin FIG. 19 is conceived. However, defect scattered light can besupplemented by the pixel B in the first rotation and defect scatteredlight can be supplemented by the pixel G in the third rotation, so thatpixel cracking can be avoided in the first and third rotations.Consequently, the case where pixel cracking always occurs can be avoidedso that lowering of S/N can be suppressed.

As described above, sub-pixel addition is performed in accordance witheach detector, and signals substantially from one and the samecoordinates in signals of respective detectors are then subjected toaddition processing. Description thereof will be made with reference toFIG. 20. FIG. 20 shows a group of detection signals substantially fromone and the same region after detection signals of detection opticalsystems 102 a, 102 b and 102 f are subjected to sub-pixel addition (inthe case where the feed pitch is equal to 8/3 pixels).

Although the original pixel size on the sample surface in each detectionsystem is 15 μm, coordinate accuracy of a resolution not larger than thepixel size can be obtained by sub-pixel addition. When the feed pitch isequal to 8/3 pixels, a pixel size of 5 μm can be obtained. In thedetection systems 102 a, 102 b and 102 f, detection signals of a region85 are added up so that a final detection signal in the region 85 can beobtained. The same rule can be applied to regions 86 and 87. Signals ofrespective detectors are added up so that final detection signals in theregions 86 and 87 can be obtained. The same rule can be applied todetection signals in other regions. Signals of corresponding regions areadded up so that a final detection signal can be obtained.

Defect determination, defect classification and defect size calculationdue to threshold processing and Haze processing due to leveldetermination are performed based on the sum signal.

Then, the defect map 160 and the Haze map 161 shown in FIG. 12 aredisplayed by the map output portion 155 through the CPU 154. The defectmap 160 is displayed based on defect type, defect size and detectioncoordinates fetched at inspection time. The Haze map 161 is displayedbased on Haze signal level and detection coordinates fetched atinspection time. The input portion 156 includes a user interface throughwhich a user can perform recipe setting etc.

A flow of defect detection processing will be described below withreference to FIG. 21.

First, a sample 1 is set on the stage and an inspection recipe is set(step 180). Inspection is started, and a defect signal and a Haze signalare detected (step 181). The position of regularly reflected light isobserved by the regularly reflected light observation optical system 105to thereby detect the magnitude and direction of change in sample height(step 182). The magnitude and direction of pixel displacement accordingto each detector are calculated by the pixel displacement detectionportion 157 based on the magnitude and direction of change in sampleheight detected in the step 182 (step 183). A coordinate correctionsignal according to each detector is generated based on the signalcalculated in the step 183 (step 184). In the coordinate correctionportion 158, coordinates of the defect signal and the Haze signal arecorrected based on the coordinate correction signal (step 185).Sub-pixel addition according to each detector is performed in the signaladdition/defect determination portion 159 (step 186). With respect tosignals of respective detectors subjected to sub-pixel addition, signalsfrom one and the same coordinates are added up (step 187). Defectdetermination, defect classification, size calculation and Hazeprocessing are performed based on the sum signal (step 188), so that thedefect map and the Haze map are displayed (step 189).

Although description has been made with reference to FIG. 15 in the casewhere only one detection optical system is located in addition tooblique illumination for performing illumination at a low elevationangle θi by way of example, a perpendicular illumination optical systemfor illuminating the sample substantially in a perpendicular directionmay be provided.

Although description has been made in the case where only one detectionoptical system 102 disposed at a detection elevation angle θs is locatedby way of example, a plurality of detection optical systems may bedisposed in directions of elevation angles. The sizes of elevationangles and the sizes of numerical apertures in the detection opticalsystems provided thus are not limited.

A plurality of detection optical systems 102 are located at differentazimuth angle directions φ as shown in FIG. 1. Elevation angles at whichthese detection optical systems 102 are disposed need not be allsubstantially the same or need not be different from one another. Theazimuth angles of arrangement of the detection optical systems 102 arenot limited likewise.

Although an example in which S3932 made by Hamamatsu Photonics K.K. isused as the PSD 52 has been described, the model type of the PSD used isnot limited.

Although description has been made with reference to FIG. 19 in the casewhere the feed pitch is equal to 8/3 pixels by way of example, any feedpitch may be used as long as the feed pitch is not an integer multipleof the pixel. The number of pixels and the pixel size are not limited.

Although description has been made with reference to FIG. 20 in the casewhere three detection systems are used by way of example, signalssubstantially from one and the same region in all detection systemsprovided thus are subjected to signal addition.

As described above, in accordance with the embodiments of the invention,detection signals of adjacent pixels are subjected to integrationprocessing, so that scattered light generated substantially from one andthe same region can be added up even in the case where pixeldisplacement occurs.

Moreover, scanning is performed in the condition that the feed pitch isshifted from an integer multiple of the pixel, and regularly reflectedlight of the laser beam irradiated on the sample is monitored to therebydetect the magnitude and direction of change in sample height, correctthe coordinates of the detection signal based on the signal and performsub-pixel addition so that scattered light signals generatedsubstantially from one and the same region can be added up accurately.

REFERENCE SIGNS LIST

1 sample, 2 laser light source, 3 beam expander, 4 polarizing element, mmirror, 5 condensing lens, 6 rotation stage, 7 translation stage, 10objective lens, 11 polarizing element, 12 image-forming lens, 1330 to 32line sensor, 1516 image surface, 20, 20′, 20″ illumination region,1721A, 21B detection range of the line sensor on the sample surface, 25,26, 27 direction of movement of the illumination region due to change insample height, 33 defect scattered light, 40 PSD, 50 detection range ofthe line sensor on the sample surface, 80 to 82, 85 to 87 detectionregion, 101 illumination optical system, 102, 102 a to 102H detectionoptical system, 103 sample stage, 104 signal processing portion, 105regularly reflected light observation optical system, 150 analogcircuit, 151 A/D conversion portion, 152 adjacent pixel integrationportion, 153159 signal addition/defect determination portion, 154 CPU,155 map output portion, 156 input portion, 157 pixel displacementdetection portion, 158 coordinate correction portion, 160 defect map,161 Haze map, 170 to 176, 180 to 189 inspection flow, 200 laser beam,201 regularly reflected light, 210 longitudinal direction ofillumination, 212 optical axis of the detection optical system, 213direction of arrangement of pixels in the line sensor

1. A defect inspection device comprising: an illumination optical systemwhich irradiates a predetermined region of an inspection target withillumination light; a detection optical system which has a detectorprovided with a plurality of pixels by which scattered light from thepredetermined region of the inspection target due to illumination lightfrom the illumination optical system can be detected; and a signalprocessing portion which has a correction portion which corrects pixeldisplacement caused by change in a direction perpendicular to a surfaceof the inspection target with respect to a detection signal based onscattered light detected by the detector of the detection opticalsystem, and a defect determination portion which determines a defect onthe surface of the inspection target based on the detection signalcorrected by the correction portion.
 2. A defect inspection deviceaccording to claim 1, characterized in that: a plurality of detectorsare provided in the detection optical system so that the detectors candetect scattered light from the surface of the inspection target indifferent azimuth angle directions with respect to the surface of theinspection target, respectively; the correction portion of the signalprocessing portion corrects the pixel displacement with respect to aplurality of detection signals based on scattered light detected by theplurality of detectors respectively; and the defect determinationportion of the signal processing portion determines a defect on thesurface of the inspection target by adding the plurality of detectionsignals corrected by the correction portion.
 3. A defect inspectiondevice according to claim 1, further comprising: a sensor which measuresa quantity of change in a direction perpendicular to the surface of theinspection target; characterized in that: the correction portion of thesignal processing portion corrects pixel displacement of the detectionsignal based on a quantity of pixel displacement calculated based on aresult of measurement by the sensor.
 4. A defect inspection deviceaccording to claim 1, characterized in that: the correction portion ofthe signal processing portion corrects the detection signal based onpredetermined patterns of the quantity of pixel displacement andcorrects pixel displacement of the detection signal based on thequantity of pixel displacement calculated based on results ofcorrection.
 5. A defect inspection device according to claim 3,characterized in that: the sensor detects regularly reflected lightreflected from a predetermined region of the inspection target; and thesignal processing portion further has a pixel displacement detectionportion which calculates a quantity of pixel displacement based on thedetected regularly reflected light.
 6. A defect inspection deviceaccording to claim 3, characterized in that: the sensor is a PSD.
 7. Adefect inspection device according to claim 1, characterized in that:the detector is a line sensor.
 8. A defect inspection method comprisingthe steps of: irradiating a predetermined region of an inspection targetwith illumination light by an illumination optical system; detectingscattered light scattered from the predetermined region of theinspection target illuminated by the illumination step, by a detectionoptical system having a detector provided with a plurality of pixels bywhich the scattered light can be detected; correcting pixel displacementcaused by change in a direction perpendicular to a surface of theinspection target with respect to a detection signal based on thescattered light detected by the detection step; and determining a defecton the surface of the inspection target based on the detection signalcorrected by the correction step.
 9. A defect inspection methodaccording to claim 8, characterized in that: the detection step detectsscattered light from the surface of the inspection target by a pluralityof detectors which can detect the scattered light in different azimuthangle directions with respect to the surface of the inspection target,respectively; the correction step corrects the pixel displacement withrespect to a plurality of detection signals based on the scattered lightdetected by the plurality of detectors respectively; and the defectdetermination step determines a defect on the surface of the inspectiontarget by adding the plurality of detection signals corrected by thecorrection step.
 10. A defect inspection method according to claim 8,further comprising the step of: measuring a quantity of change in adirection perpendicular to the surface of the inspection target by asensor; characterized in that: the correction step corrects pixeldisplacement of the detection signal calculated based on a result ofmeasurement in the change quantity measuring step.
 11. A defectinspection method according to claim 8, characterized in that: thecorrection step corrects the detection signal based on predeterminedpatterns of a quantity of pixel displacement and corrects pixeldisplacement of the detection signal calculated based on results ofcorrection.
 12. A defect inspection method according to claim 10,further comprising the steps of: detecting regularly reflected lightreflected from a predetermined region of the inspection target by thesensor; and calculating a quantity of pixel displacement based on thequantity of change measured by the change quantity measuring step.
 13. Adefect inspection method according to claim 10, characterized in that:the sensor which measures the quantity of change in the directionperpendicular to the surface of the inspection target in the changequantity measuring step is a PSD.
 14. A defect inspection methodaccording to claim 8, characterized in that: the detection step detectsscattered light from the predetermined region of the inspection targetdue to illumination light of the illumination optical system by a linesensor.
 15. A defect inspection method according to claim 9, furthercomprising the step of: translationally moving the inspection target bya predetermined pitch, characterized in that: the predetermined pitch inthe translational moving step has a size different from an integermultiple of a pixel number of one pixel in the detector; and thecorrection step applies addition processing to the detection signals inaccordance with each pixel which detects scattered light substantiallyfrom one and the same region of the inspection target.
 16. A defectinspection method according to claim 15, characterized in that: thecorrection step performs addition processing while shifting the pixelsof the detection signals by intervals of (1/a size of pixels in thedetector)×(the predetermined pitch).